Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive Income (Loss), Net [Member]
Balance at Dec. 31, 2019	$ 3,467,685		$ 309,513	$ 1,736,664	$ 1,476,232		$ (54,724)
Balance, Shares Issued at Dec. 31, 2019			92,947
Net income (loss)	(45,174)				(45,174)
Other comprehensive income (loss)	134,793						134,793
Comprehensive income (loss)	89,619				(45,174)		134,793
Cash dividends declared	(95,605)				(95,605)
Common stock activity, long-term incentive plans	17,855			17,715	140
Issuance of stock from dividend reinvestment and stock purchase plans	4,164			4,164
Net settlement of accelerated share repurchase agreement (1,001,472 shares)	12,110			12,110
Repurchase of common stock	(12,716)			(12,716)
Balance at Dec. 31, 2020	3,439,025	$ (44,087)	$ 309,513	1,757,937	1,291,506	$ (44,087)	80,069
Balance, Shares Issued at Dec. 31, 2020			92,947
Net income (loss)	463,215				463,215
Other comprehensive income (loss)	(134,004)						(134,004)
Comprehensive income (loss)	329,211				463,215		(134,004)
Cash dividends declared	(95,927)				(95,927)
Common stock activity, long-term incentive plans	15,967			15,688	279
Issuance of stock from dividend reinvestment and stock purchase plans	3,872			3,872
Repurchase of common stock	(21,796)			(21,796)
Balance at Dec. 31, 2021	$ 3,670,352		$ 309,513	1,755,701	1,659,073		(53,935)
Balance, Shares Issued at Dec. 31, 2021	92,947		92,947
Net income (loss)	$ 524,089				524,089
Other comprehensive income (loss)	(718,247)						(718,247)
Comprehensive income (loss)	(194,158)				524,089		(718,247)
Cash dividends declared	(94,891)				(94,891)
Common stock activity, long-term incentive plans	16,640			16,498	142
Issuance of stock from dividend reinvestment and stock purchase plans	3,577			3,577
Repurchase of common stock	(58,892)			(58,892)
Balance at Dec. 31, 2022	$ 3,342,628		$ 309,513	$ 1,716,884	$ 2,088,413		$ (772,182)
Balance, Shares Issued at Dec. 31, 2022	92,947		92,947